$ E = \left[\begin{array}{rrr}0 & 2 & 1 \\ 0 & 1 & 0 \\ 2 & 0 & 1\end{array}\right]$ What is $ E^{-1}$ ?
$ = \left[\begin{array}{rrr}-\frac{1}{2} & 1 & \frac{1}{2} \\ 0 & 1 & 0 \\ 1 & -2 & 0\end{array}\right]$